The present invention relates to the general field of turbine engine compressors. It more particularly relates to a high pressure turbine engine compressor in which air recirculation is provided aiming at limiting the pumping phenomenon.
A turbine engine compressor comprises several successive compression stages, each compression stage consisting of a row (or grid) of fixed vanes followed by a row of mobile vanes. An annular housing surrounds the rows of vanes and delimits on the outside the outflow jet of the airflow passing through the compressor.
Such a compressor is subject to pumping. The pumping is a phenomenon for which minimization is sought within a turbine engine since this is expressed by sudden oscillations of the air pressure and of the airflow rate, which subject the vanes of the compressor to considerable mechanical stresses which may lead to their embrittlement, or even to their failure. This phenomenon notably occurs at the vane head, at the limiting air layer present between the head of the vanes and the housing of the compressor and is locally expressed by lower pressure pockets.
One of the solutions known for minimizing this phenomenon is to provide air recirculation within the compressor. For this purpose, air is generally taken from the outflow jet of the compressor at right angles (or just downstream) to the head of mobile vanes of a compressor stage. This taken air then transits into a conduit before being re-injected more upstream in the outflow jet, for example upstream and towards the head of mobile vanes of another stage of the compressor. For example, reference may be made to documents US 2005/0226717 and U.S. Pat. No. 5,474,417 which describe exemplary embodiments of such air recirculation.
The re-injection of air taken from the outflow jet is generally accomplished by means of air injectors which are mounted in recesses provided for this purpose on the housing surrounding the vanes. Typically, these air injectors are parts regularly spaced out angularly from each other and each provided with an internal air injection channel opening out, on one side into the outflow jet of the compressor, and on the other side towards an air supply conduit connected to the air recirculation circuit.
Maintaining these air injectors in position on the housing of the compressor poses problems. Indeed, known solutions either consist of mounting the air injectors in their recess by a tight adjustment of the H7p6 type, or of immobilizing the air injectors in their recess by means of screws. Now, the mounting of the air injectors by tight adjustment has the main drawback of making it impossible to disassemble these injectors without causing damages to the housing. As to maintaining the injectors by means of screws, application problems are posed as regards the size and the number of required screws (one to two screws per air injector), without counting the occupied space which would need to be available for inserting a self-braking means on the housing.